当角的终边在第二象限时,a=3π/4+2kπ,k∈Z.2sina+cosa=2sin(3π/4+2kπ)+cos(3π/4+2kπ)=2sin(3π/4)+cos(3π/4)=√2-√2/2=√2/2当角的终边在第四象限时,a=-π/4+2kπ,k∈Z.2sina+cosa=2sin(-π/4+2kπ)+cos(-π/...